Electroplating has heretofore been conducted by mounting collector rings (referred to as C rings hereinafter) on both shaft ends of a conductor roll (referred to as a CDR hereinafter), and applying a current through brushes. For the purpose of maintaining the plating stability and the stabilized operation, it is important to ensure the current-conducting properties in the collector portions while it is naturally important to maintain the surface properties of the CDR body directly contacted with a steel strip.
Conventional CDRs each have cast Cu-made C rings which are larger than the diameter of the steel-made roll shaft and which are mounted on the right and left roll shaft ends, and an electric current is applied to the C rings. The conventional CDRs, therefore, have the following problems (1) to (3).
(1) Poor contact between the C rings and the roll shaft often produces burning troubles of brushes, etc.
That is, application of a current to a poor contact portion formed by improper maintenance of the roll shaft, improper mounting of the C rings, or the like, results in generation of heat in a large quantity which makes the poor contact portion reach a high temperature. A thermal expansion difference between the C rings and the roll shaft arises because the materials are different. Since the amount of thermal expansion of the C rings is larger than that of thermal expansion of the roll shaft, the poor contact between the C rings and the roll shaft is worsened. The balance of currents uniformly flowing in the C rings mounted on the right and left roll shaft ends is destroyed due to the poor contact between the C rings and the roll shaft caused by such improper maintenance and mounting, and application of the currents. As a result, a large current flows on the C ring side which has a smaller contact resistance, and the brushes and the lead wires of the C ring side may be burned.
(2) The operation burden of removal and installation of the C rings, and adjustment of the sliding contact, becomes heavy during the repairing operation of the roll body.
(3) The life of the sliding collector parts, such as the C rings and the brushes, is short due to their wear.